1. Field of the Invention
The present invention relates to an acrylic derived adhesive used for attachment of polarizing plate, to the acrylic derived adhesive for polarizing plate excellent in long-term preservation quality, and to an optical member using the adhesive.
2. Description of the Prior Art
In liquid crystal display (LCD), a constitution is generally used in which a polarizing plate, an elliptically polarizing plate, a polarizing plate with a compensating film, a polarizing plate with reflective/transflective layer, and a polarizing plate with a brightness enhanced film are laminated onto a liquid crystal cell through adhesive. In manufacturing method of such LCD, for the purpose of preventing of variation in quality, and of improving efficiency of LCD assembly line, etc., a method is used in which optical member is adhered onto a liquid crystal cell in a state where adhesive layer is applied beforehand thereon. In that case, as adhesive, acrylic derived adhesive that is excellent in optical transparency, shows moderate tacky adhesive properties, such as wettability and cohesiveness, and is excellent in weatherability, heat resistance, etc. is widely used. In addition, an acrylic derived adhesive is an adhesive that has acrylic derived polymer as base polymer, and usually, since a peroxide may be used in polymerization of the acrylic derived polymer, the adhesive contains a residual component originating in peroxide.
However, it is known that when long time passes until a polarizing plate is used for attachment after an acrylic derived adhesive is applied on the polarizing plate, physical properties of the adhesive may change or adhesive strength may be decreased after attached on a liquid crystal display, and then peeling may be observed in a durability examination. A cause of change in physical properties of the adhesive is not clarified until now, and an effective index for improving long-term preservation quality of the adhesive is not obtained.
Then, an object of the present invention is to provide an adhesive for polarizing plate that is excellent in long-term preservation quality, and an other object of the present invention is to provide an optical member using the adhesive.